Seal assemblies for water well casings

ABSTRACT

An economical easily installable and easily removable seal assembly for use on water well casings comprises a dome having a central shaft threaded through a lower flange means so that rotation of the shaft compresses a rubber ring between the flange means and a lower rim of the dome, radially expanding the ring to grip the inside of a well casing with uniform pressure around the periphery of the ring, and also compresses an upper ring between the dome and the shaft.

United States Patent Martin Nov. 4, 1975 SEAL ASSEMBLIES FOR WATER WELL3,306,362 2/1967 Urbanosky 277/166 CASINGS 3,627,334 12/1971 Reddy277/166 3,758,072 9/1973 Herd 277/188 [76] Inventor: Carlyle J. Martin,Pierce Creek g g g Bmghamton Primary ExaminerRobert J. Smith Attorney,Agent, or Firm-Richard G. Stephens [22] Filed: Aug. 1, 1974 21 Appl.No.: 493,526 ABSTRACT An economical easily installable and easilyremovable 52 US. Cl seal assembly for use on Water casings comprises EInt z gi z ig a dome having a central shaft threaded through a [58]Field of S E a 110 in lower flange means so that rotation of the shaftcompresses a rubber ring between the flange means and a lower rim of thedome, radially expanding the ring to [56] References Cited grip theinside of a well casing with uniform pressure around the periphery ofthe ring, and also compresses UNITED STATES PATENTS an upper ringbetween the dome and the shaft. 2,703,7l9 3/1955 Crothers 277/1103,260,499 7/1966 Roeme r 277 110 11 Claims, 6 Dfawlng Flgules l6 lo I 7r I 8 l3c l3b Kid 28 [3a 13f lld /1 28a llc llc

2|e T E 2Id 21d 2 7 I U.S. Patent Nov. 4, 1975 Sheet2of3 3,917,292

F/G. a

SEAL ASSEMBLIES FOR WATER WELL CASINGS My invention relates to improvedseals for the upper ends of the casings of water wells, and moreparticularly, to improved seals which are easier to install and remove,and which are economical to fabricate.

Water wells utilized at suburban and rural residences in a large part ofthe United States ordinarily use a well casing, typically comprisingplural sections of pipe 5 to 7 inches in diameter, which are welded (orthreaded) together to extend 50 to 500 feet down into the earth to awater layer. A submersible electric motor-driven pump is immersed in thewater layer near the bottom of the casing, being suspended from near thetop of the casing by a water pipe, typically 1 inch in diameter, upwhich water is pumped. In geographical locations which are not frostfree, the water pipe-ordinarily extends outwardly through the side ofthe well casing two or three feet below ground level and then is routedunderground to the residence. The upper end of the well casing extendstypically 6 to 18 inches above ground level, so that ground surfacewater may not run into the casing and contaminate the well. It isnecessary that an air passage or vent be provided near the top of thewell casing, so that pumping of water from the well not create a partialvacuum inside the well casing to prevent or impede water delivery. It isalso necessary that an opening be provided near the top of the casingfor an electrical cable needed to supply power to the motor of thesubmersible pump. It is important that such openings not allow rainwater, vermin or insects to enter the well casing. While simple devicessuch as a plate with the required openings conceivably could bepermanently welded or otherwise affixed to the top end ofa well casing,the fact that the motor-pumps fail and sometimes must be replaceddictates that some form of removable seal or cap be provided, andvarious forms of removable well seals or caps are presently widely used.

Some well casings use successive threaded sections of pipe, while othershave successive sections welded together. While it is theoreticallypossible in threaded casing installations to provide a removable wellcap which threadedly engages threads provided at the upper end of thewell casing, caps which thread into the well casing are deemedimpractical for a number of reasons. Turning a threaded cap to installit would undesirably twist the electrical cable which must pass throughit, unless the cable passed through an opening in the cap so large thatinsects or rainwater could also pass through the opening. Also,prohibitively great forces often would be required to unscrew a threadedcap which had been exposed to weather for some years. For such reasons,practical removable well caps cannot be threaded onto the upper ends ofwell casings, and the well caps in common use instead use sealsincluding rubber rings which may be tightly clamped to the upper end ofa well casing.

Various known well seals comprise plural metal plates or rings betweenwhich a rubber seal ring is disposed, with means for clamping the platesvery tightly together to radially expand the rubber ring, whereby therubber ring is pressed tightly against the inside or the outside of thewell casing. To insure that 'the rubber seal is adequately compressedaround its entire periphery so as to form a watertight seal, the priorseals use a number of bolts spaced around the seal, each of which mustbe tightened with substantial force. Several important disadvantages ofprior seals stem from their use of a plurality of bolts, or plurality ofbolts and nuts. The bolts and nuts frequently must be installed underadverseclimatic conditions. If bolts or nuts are accidentally droppedthey are frequently lost in mud, snow or the like at a well site. Also,the drive shoe of a welldrilling rig often provides a hole in the earthexceeding the outer diameter of the well casing, leaving a spacesurrounding the casing in which bolts and nuts may be irretrievably lostshould they be accidentally dropped therein. One object of the presentinvention is to provide an improved seal assembly of a single-piecenature', i.e., which does not require the tightening and loosening of aplurality of bolts and or nuts to install or remove the assembly. Byprovision of a single bolt means, the present invention allows a sealassembly to be installed or removed much more rapidly than priorassemblies, thereby providing a significant savings in labor costs.

As well as beinglost during installation, well seal assemblies whichutilize numerous bolts and nuts are disadvantageous because such partsare sometimes lost or mis-placed between the factory and the well site.One object of the invention is to provide a well seal assembly which maybe completely assembled at the factory, and which then need not later bedisassembled to allow its installation atop a well casing.

Prior art seal assemblies which use a plurality of bolts and/or nutsspaced around the seal are also disadvantageous in that their threadssometimes become jammed or may be inadvertently stripped, sometimesruining a seal assembly unless it is re-bored and re-tapped with alarger threaded hole, or sometimes requiring that spare bolts or nuts beobtained. Another object of the invention is to provide an improved sealassembly which obviates such problems.

A further disadvantage of seals using plural bolts and nuts spacedaround the seal is that they must be tightened evenly, i.e., bytightening a given bolt only partially and then proceeding to similarlytighten each of the other bolts before further tightening the givenbolt, or else the seal assemblies, which frequently are made of castiron, may fracture. Another disadvantage is that provision of pluralindependent bolts may cause the seal to grip tightly at some placesaround its periphery, but to grip much less tightly at other places, sothat leaks may occur. An additional object of the invention is toprovide an improved well seal assembly which does not require sequentialtightening of a plurality of bolts and/or nuts, and a further object ofthe invention is to provide an improvedwell seal assembly whichautomatically expands a seal ring evenly around its entire periphery asa single bolt means is tightened.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts, which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a side elevation view in cross-section of a preferred form ofthe present invention.

FIG. 2 is a side elevation view in cross section illustrating onepossible modification of the device of FIG. 1.

FIG. 3 is a side elevation view in cross-sectionof one alternativeembodiment of the invention.

FIG. 4 is a side elevation view in cross-section of a further form ofthe invention.

FIG. 4a is a plan view showing several portions of the assembly of FIG.4; and

FIG. 5 is a side elevation view in cross-section illustrati ng onepossible modification of the device of FIG. 1.

In FIG. 1 the upper end of a section of well casing pipe is shown at 10.The improved seal assembly comprises a dome 1 l of generallyhemispherical shape having an annular groove, the upper surface 11a ofwhich sits atop the upper end of casing 10. An annular outer flange 11bextends below surface 11a, forming a drip edge, so that water runningdown the outside of dome 11 cannot enter the well casing. An innerannular flange lle-extends downwardly into the casing a short distance,as shown. The width of the groove between flanges 11b and 110 is notcritical, and is madeto exceed the wall width of standard casing pipe,so that the dome may be laid atop the casing without the need for apress-fit. The outer surface of inner flange 110 is preferably madeslightly less (e.g., one-sixteenth inch) than the inside diameter ofcasing so that placing dome 11 atop the casing accurately aligns thedome with the casing. Inasmuch as the seal assembly grips the inside ofthe well casing, it is immaterial whether the exterior of the wellcasing is threaded or not.

The water pipe extends from the pump (not shown) near the bottom of thewell casing to a point about 3 feet below the top of the casing, where aknown form of device known as a pitless adapter (not shown) supports theweight of the water pipe and pump and allows the water pipe to extendlaterally through the wall of the casing, from where it may rununderground to the residence. Dome 11 is provided with a tapped hub at28a which accommodates a threaded nipple for a standard conduit or cablefitting 28, through which wires or electrical cable (not shown) maypass, with the cable extending down the inside of the well casing to themotor-pump. A removable plug 26 is also preferably threaded into atapped hole through dome ll.

Dome 11 is provided with a central upper bore 12 through which the lowerportion of shaft 13 passes. Bore 12 need not closely correspond indiameter with the portion of shaft 13 passing through it, and indeed ispreferably made somewhat oversize, so as to allow an appreciable amountofrocking of the axis of shaft 13 relative to the axis of bore 12. Thelower face 13a of a widened portion 13b of shaft 13 sits atop metalwasher 14, which in turn sits atop rubber (or other elastomeric) washer15, washers 14 and 15 being situated in a circular recess 11d in the topof dome 11. If desired, portion 13b of shaft 13 may be provided with adepending flange of the nature shown in dashed lines at 13f, to preventthe accumulation of water on washers 14 and 15, although such arefinement is deemed ordinarily unnecessary. The upper reduced-diameterportion 13c of shaft- 13 is threaded to engage internal threads in thedepending hub portion 16a of vent cap 16. Cap 16 comprises a generallyhollow dome portion 16b connectedto hub 16a by a plurality of ribs sothat air may flow between the interior of hub portion 16a and theoutside of cap 16, through a screen 17 situated inside dome 16b atop hubportion 16a of cap 16. Shaft 13 includes a central bore or passage 13dwhich extends downwardly from the upper end of the shaft to a point hub21a may also tilt slightly relative to the axis of shaft inside dome 11,and a laterally extending passage 13a. The upper end of passage 13d ispreferably threaded to receive a small plug 18. I

A length of the lower'end of shaft 13 is threaded to engage the internalthreads of hub 21a of a lower flange means 21, which integrally includesan annular ring portion 21b and an annular lower flange 21c supported byand spaced from hub 21a by a plurality of armsor web members 21d, onlytwo ofwhich are visible in FIG.

1. The electrical cable (not shown) may pass between a pair of the webmembers to reach the pump near the bottom of the well. The lower flangemeans 21 cornprised of portions 21a-21d is preferably cast as a singlepiece. A laterally extending pin 23 is either threaded or permanentlystaked in a hole near the lower end of shaft 13. With pin 23 in place,it will be seen that the entire assembly may be carried in one piece,i.e., that no loose parts such as additional nuts and/or bolts arerequired and susceptible to loss or mis-placement prior to placement ofthe assembly atop the well casing. An annular rubber (or otherelastomeric) ring 25 sur: rounds ring 21 b. It may be noted that neitherhub portion 21a nor shaft 13 need be threaded with extremely precisethreads.

Section 13b of shaft 13 is preferably provided with a cylindricalperiphery so that it may be gripped by an ordinary pipe wrench, althoughit may be provided with flatsurfaces to allow alternative use of anotherform of wrench. As shaft 13 is rotated by a wrench, lower flange means21 will be seen to be drawn upwardly, assuming that it does not rotatewith shaft 13. If, before the assembly is seated atop the well casing,lower flange 21 is lightly screwed up shaft 13 so as to slightly engageand squeeze rubber ring 25, sufficient friction will be provided betweenring 25 and lower flange means 21 that the latter will not rotate asshaft 13 is rotated. As screw 13 is rotated, ring 25 then will becompressed tightly between the upper face 21e of lower flange 21c andthe lower face lle of inner flange 11c, and due to the compressibilityof ring 25, portions of it will be urged radially outwardly against theinside wall of the well casing 10, and portions of it will be urgedradially inwardly against the vertical outer face of ring portion 21b.Rotation of screw 13 causes lower flange means 21 to apply a very largeupward force to dome 11 through ring 25, but also causes shaft portion13b to i apply an equal downward force to dome 1 1 via washers 14 and15, with the result that no appreciable net vertical force is applied todome 11, and it continues to rest atop the well casing 10, with theweight of the pipe wrench tending to hold it atop casing 10 as shaft 13is rotated. Because of the tremendous mechanical advantage obtainable bymeans of the threads on screw 13,

sufficient compression to securely lock the seal assem-- bly in the endof casing 10 is readily achieved. As screw 13 is rotated to lock theseal assembly in place, the downward pull on shaft 13 will be seen tocause face 13a of shaft 13 to press metal washer .14 downwardly,compressing rubber washer 14, thereby to provide a watertight seal atthe top of dome 11.

As compression of ring 25 expands the ring radially inwardly andoutwardly, the ring will tend to be compressed with equal pressuresagainst ring 21b and the inside of the well casing at all locationsaround the periphery of the ring 25. Due to the slight oversize of bore12, shaft 13may pivot slightly in bore 12 so as to tend to equalize thecompressive forces all around the ring,

5. l3, and the lower portion of shaft 13 may deflect slightly, so thatequal forces are applied around the entire seal, even if none of thementioned portions of the assembly are machined to close tolerances.

If and when it becomes necessary to remove the seal assembly, so as towithdraw the motor-pump, for example, the seal assembly may be easilyremoved by rotating shaft 13 in the reverse direction by means of awrench, thereby lowering lower flange means 21 so that rubber ring 25 isno longer compressed by' it, and then the assembly may be lifted off ofthe casing. After long usage, the rubber ring 25 may tend to stick tothe inside of the casing even if it is no longer being squeezed. One ora few upward hammer blows on flange 11b of the dome readily breaks therubber ring loose from the inside of the casing. As the assembly islifted from the casing, flange 21c lifts the rubber ring out of thecasing, lifting all portions of it even if it should be broken intoseveral pieces, so that none of the pieces fall down inside the casing.

Well seal assemblies are frequently removed, after many years of use, bypersons who are not familiar with the internal construction of suchseals, and if bolts which tighten various prior art seals are loosenedtoo much, nuts or other parts may drop down inside the well casing andbe irretrievably lost. Provision of pin 23 on shaft 13 below lowerflange means 21 prevents an unknowing person from turning shaft 13 so asto screw shaft 13 entirely out of hub 21a. An extreme turning of shaft13 in the reverse direction will lower flange means 21 no more than towhere it jams against pin 23, and then continued rotation of shaft 13will merely rotate lower flange means 21 without further lowering it.Hence it will be clear that no parts of the assembly can drop downinside the well casing.

A further feature of the invention is its versatility in allowing thewell to be vented in a variety of different ways. If plug 18 is removed,venting may occur through vent cap 16 and passages 13d, 13e.Alternatively, in some applications, such as where it is preferred thata vent line be attached leading from an area (such as from inside aresidence) where a preferred'source of air is located, plug 18 may beleft in place and plug 26 removed, and replaced by a conventional tubingconnector. In some applications both plugs 18 and 26 may be left inplace and venting allowed to occur through conduit or cable fitting 28and any conduit (not shown) connected thereto.

In amodified seal assembly partially shown in FIG. 2, hub 21a of thelower flange means 21 is provided with an oversize central bore 30, anda nut 31 is threaded onto shaft 13 below hub 21a. The upper face of nut31 may be slightly convexly rounded (and is shown in FIG. 2 with anexaggerated roundness), and/or, if desired, the lower face of hub 21amay be similarly rounded concavely. As shaft 13 is rotated to raise nut31 and lower flange means 21', the latter may tilt slightly, so that thelower flange means applies the same upward pressure to the rubber ring(not shown in FIG. 2) at all locations around the ring. Because nut 31does not frictionally engage the side of the well casing, it isnecessary before installing the assembly of FIG. 2 that nut 31 betightened enough that friction between hub 21a and nut 31 prevent thelatter from turning as screw 13 is turned.

A further modified seal assembly shown in FIG. 3 includes a dome 11which is provided with a pair of concentric annular grooves 11a' and11a", so that the 6 dome may be installed on either of two distinctlydifferent diameters of well casing. In FIG. 3 the upper hub portion ofthe dome through which shaft 13' extends is situated inside the domerather than outside as in FIG.

1. Shaft 13 is provided with an internal threaded bore into which bolt24 extends. The wide head of bolt 24 lies against the lower surface oflower plate means 21 A plurality of holes 21d, 2111' are provided inplate means 21' to allow electrical wires to pass therethrough. Thelower edge of flange 11c and an outer edge 21c of plate means 21 areshown beveled or chamfered, and as shaft 13 is rotated to pull bolt 24and plate 21 upwardly, thebeveled surfaces tend to press rubber ring 25'principally outwardly against the casing 10. A length of bolt 24 iscounterbored as shown, and after bolt 24 is threaded into shaft 13 pin23' (or a set screw) is inserted in a hole through shaft 13. The pin 23will be seen to act as a limit stop, preventing bolt 24 from beingentirely threaded out of shaft 13', so that bolt 24 and plate means 21'will not drop down the well casing no matter how much one rotates shaft13 to loosen the seal assembly. In order to use the assembly of FIG.'3with the larger diameter well casing for which it isalso designed, oneneed merely provide a plate means 21 of larger outside diameter thanthat shown.

Ina further modified embodiment of the invention shown in FIG. 4 thedome of the assembly in actuality comprises a substantially flat cap 41having a threaded central bore through which hollow screw shaft 43 isthreaded. The lower end of shaft 43 engages a ring-shaped boss 51a onplate means 51. As shaft 43 is turned into cap 41, by rotating theconduit fitting 60, for example, into which the upper end of shaft 43 isthreaded, plate 51 is urged downwardly relative to the cap, compressingrubber ring 55 against lower ring 56, and hence radially expanding ring55 so that it will engage the well casing. The outer edge of plate 51and the upper surface of ring 56 are preferably beveled in the mannershown in FIG. 3, to prevent much of the rubber from being pushedinwardly. Metal lower ring 56 is suspended or prevented from loweringrelative to cap 41 by a plurality of arms 57, 57 which are fastened attheir upper ends to cap 41, and which extend downwardly through holes orarcuate slots in plate 51 and then radially outwardly to engage theunderside of ring 56. Only two arms 57 are shown in FIG. 4, but a largernumber may be used, 'all preferably spaced equidistantly apart aroundthe assembly. In FIG. 4 four arms 57 are shown extending throughrespective arcuate slots 51b in plate 51. Neither ring 56 nor ring 55are shown in FIG. 4a. Arms 57 are shown fastened to cap 41 by means ofscrews 58, 58, which are preferably countersunk, provided with no driveslot, and painted over, and indeed screws 58 and/or arms 57 may bewelded to cap 40 once they have been inserted through slots 51b in plate51. Alternatively, sheet metal retaining clips 59 may be inserted onarms 57 aboveplate 51 so that no arm may fall into casing 10 even ifscrews 58 are allowed to be loosened.

FIG. 5 illustrates a portion of modified embodiment which otherwise isconstructed in accordance with FIG. 1, but wherein two separate rubberrings 25a, 25b are compressed between the lower flange means and flange11:: of hub 11, with a metal ring 19 interposed between the two rubberrings.

It should be noted that the invention may be used to seal well casingsused with jet pumps, and various other 7 pumps, as well as submersibleelectric motor driven pumps, and also may be used to seal pumpout pipesof septic tanks.

It is important to note that various of the features shown may be usedin combinations other than those shown in the drawings. For example,chamfered surfaces engaging the rubber ring 25 may be used in FIG. 1,the double ring arrangement of FIG. may be used with the otherembodiments in addition to that of FIG. 1, the cap or dome of FIG. 1 mayincorporate a pair of concentric annular grooves of the type shown inFIG. 3, etc.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A well seal assembly for sealing the upper end of a hollowcylindrical well casing, comprising, in combination: a cap having afirst annular surface adapted to seat on said end of said casing, anannular first flange adapted to extend into said casing adjacent theinner wall of said casing, and a bore extending through said capsubstantially along the cylindrical axis of said casing; shaft meansextending through said bore of said cap means; a lower flange meansadapted to be situated within said casing and be supported by said shaftmeans, said lower flange means having an annular surface extending belowsaid annular first flange; a compressible seal ring situated betweensaid first flange and said surface of said lower flange means; and athreaded connection between said shaft means and said lower flangemeans, whereby rotation of said shaft means may raise said lower flangemeans to compress said compressible seal ring between'said first flangeand said lower flange means, causing radial expansion of said seal ringagainst said inner wall of said casing.

2. An assembly according to claim I wherein said threaded connectioncomprises mating screw threads on a lower end portion of said shaftmeans and on a hub portion of said lower flange means.

3. An assembly according to claim 1 wherein said shaft means extendsslidingly through an opening in said lower flange means, nut means aresituated on said.

shaft means below said lower flange means, and said threaded connectioncomprises mating screw threads on a lower end portion of said shaftmeans and said nut means.

4. An assembly according to claim 1 having bolt means extending upwardlyfrom said lower flange means, and said threaded connection comprisesmating screw threads on said bolt means and said shaft means.

5. An assembly according to claim 1 having stop means to limit operationof said threaded connection to limit lowering of said lower flangemeans.

6. An assembly according to claim '1 having a second compressible sealring between said first flange and said lower flange means, and asubstantially incompressible ring situated between compressible sealring andsaid second compressible seal ring.

7. An assembly according to claim 1 wherein said cap includes a hubportion carrying said bore, said hub portion having a flat upper surfaceportion, said shaft below said upper end of said casing adjacent theouter wall of said casing.

10. An assembly according to claim 1 wherein said cap means comprises agenerally hemispherical hollow cap having at least one threaded openingthrough the wall thereof.

11. An assembly according to claim 2 wherein lower flange meanscomprises a ring-shaped portion carrying said annular surface, a hubportion threaded on said.

shaft means, and rigid means interconnecting said ringshaped portion andsaid hub portion, said rigid means containing at least one openingallowing passage of electrical wiring through said opening.

1. A well seal assembly for sealing the upper end of a hollowcylindrical well casing, comprising, in combination: a cap having afirst annular surface adapted to seat on said end of said casing, anannular first flange adapted to extend into said casing adjacent theinner wall of said casing, and a bore extending through said capsubstantially along the cylindrical axis of said casing; shaft meansextending through said bore of said cap means; a lower flange meansadapted to be situated within said casing and be supported by said shaftmeans, said lower flange means having an annular surface extending belowsaid annular first flange; a compressible seal ring situated betweensaid first flange and said surface of said lower flange means; and athreaded connection between said shaft means and said lower flangemeans, whereby rotation of said shaft means may raise said lower flangemeans to compress said compressible seal ring between said first flangeand said lower flange means, causing radial expansion of said seal ringagainst said inner wall of said casing.
 2. An assembly according toclaim 1 wherein said threaded connection comprises mating screw threadson a lower end portion of said shaft means and on a hub portion of saidlower flange means.
 3. An assembly according to claim 1 wherein saidshaft means extends slidingly through an opening in said lower flangemeans, nut means are situated on said shaft means below said lowerflange means, and said threaded connection comprises mating screwthreads on a lower end portion of said shaft means and said nut means.4. An assembly according to claim 1 having bolt means extending upwardlyfrom said lower flange means, and said threaded connection comprisesmating screw threads on said bolt means and said shaft means.
 5. Anassembly according to claim 1 having stop means to limit operation ofsaid threaded connection to limit lowering of said lower flange means.6. An assembly according to claim 1 having a second compressible sealring between said first flange and said lower flange means, and asubstantially incompressible ring situated between compressible sealring and said second compressible seal ring.
 7. An assembly according toclaim 1 wherein said cap includes a hub portion carrying said bore, saidhub portion having a flat upper surface portion, said shaft meansincludes a widened shaft portion having a diameter exceeding that ofsaid bore, said widened shaft portion having an annular lower surface;and washer means situated between said flat upper surface portion andsaid annular lower surface.
 8. An assembly according to claim 1 whereinsaid shaft means includes an internal passageway extending from aportion of said shaft means below said bore to a portion of said shaftmeans above said bore.
 9. An assembly according to claim 1 wherein saidcap includes an annular second flange adapted to extend below said upperend of said casing adjacent the outer wall of said casing.
 10. Anassembly according to claim 1 wherein said cap means comprises agenerally hemispherical hollow cap having at least one threaded openingthrough the wall thereof.
 11. An assembly according to claim 2 whereinlower flange means comprises a ring-shaped portion carrying said annularsurface, a hub portion threaded on said shaft means, and rigid meansinterconnecting said ring-shaped portion and said hub portion, saidrigid means containing at least one opening allowing passage ofelectrical wiring through said opening.